The inventive concept relates generally to a semiconductor memory, and more particularly, to a nonvolatile memory device and a method of programming the nonvolatile memory device.
Semiconductor memory devices can be roughly classified into two categories according to whether they retain stored data when disconnected from power. These categories include volatile memory devices, which lose stored data when disconnected from power, and nonvolatile memory devices, which retain stored data when disconnected from power. Examples of volatile memory devices include static random access memory (SRAM), dynamic random access memory, and synchronous DRAM (SDRAM). Examples of nonvolatile memory devices include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable and programmable ROM (EEPROM), flash memory device, phase-change RAM (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM), and ferroelectric RAM (FRAM).
In an effort to improve the storage capacity and performance of nonvolatile memory devices, researchers are continually seeking to increase their integration density. One recent approach to increasing integration density involves forming nonvolatile memory cells in a three-dimensional structure on a substrate. In such a structure, multiple memory cells are typically stacked in a direction perpendicular to the substrate. The development of such structures presents many technical challenges that can affect both device performance and manufacture. Accordingly, researchers continue to devote substantial resources to develop improved three-dimensional nonvolatile memory devices.